Gas temperature measurements by laser spectroscopic techniques and by optical emission spectroscopy

H-atom temperatures were measured using two-photon allowed transition laser induced fluorescence in a microwave plasma reactor used for diamond deposition. These temperatures are compared with the rotational temperatures of ground state molecular hydrogen, equal to the gas temperature, measured previously by coherent anti-stokes Raman spectroscopy. We observed an excellent agreement between the two temperatures. Rotational temperatures of the G(1) Sigma{g}(+) electronically excited state of molecular hydrogen were also obtained by measuring the relative line intensities in emission of the R-branch of the G(1) Sigma(g)(+)-->B-1 Sigma{u}(+) (0,0) band by optical emission spectroscopy. These measurements yielded lower temperatures than the gas temperature by 550 K, but followed its variation as a function of the power density. We defined then T-R(G(1)-->{g}(+)) as a spectroscopic parameter useable for optimizing and monitoring the plasma conditions for diamond deposition, within the range of conditions tested here.